It is known that, if an impedance of an antenna of an electronic device is well matched, a loss that a current (e.g., a signal) transmitted from a transmission/reception circuit without being radiated through the antenna and may have a value less than or equal to a predetermined range. On the other hand, if an object having a permittivity, such as a hand or a head, is in proximity to the antenna, a change in the permittivity may occur in the vicinity of the antenna, causing a shift (or transition) of a resonant frequency of the antenna. If the impedance of the antenna is mismatched, the loss that a current transmitted from the transmission circuit is returned without being radiated through the antenna may have a value greater than or equal to a predetermined range. The electronic device may control its impedance matching circuit based on the signal that is returned without being radiated.
In case of a tunable antenna-based electronic device, when transmitting a signal for data transmission, the electronic device may obtain a return loss for the transmitted signal to control an impedance of the impedance matching circuit. However, the electronic device cannot control its tunable antenna during the time period (e.g., the idle mode or idle state) in which the electronic device does not perform data communication with an external device such as a base station.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.